Agricultural harvester vehicles are often employed in the field with implements such as draper platforms or windrowers to sever crop plants from the ground and alternatively gather them for further processing.
These reciprocating knives are in the general form of an elongate cutter bar including one or more elongate reciprocating members to which a plurality of triangular knife blades is fixed. The reciprocating knife blades are translated back and forth at high speed such that they pass through slots in stationary knife guards. The relative movement of the blades in the knife guards works like a row of scissors to sever the plant stalks. The severed portions of the plants typically fall backward onto a gathering mechanism such as a lateral conveyor. The lateral conveyor, disposed immediately behind the reciprocating knives, carries them to a central region of the implement from which they are further conveyed to the agricultural harvester, or are deposited on the ground.
In one common arrangement, a single reciprocating gearbox is disposed at one end of the implement and drives a single reciprocating knife that extends the entire width of the implement. An example can be seen in U.S. Pat. Nos. 4,267,689 or 6,510,681. This arrangement is satisfactory for a narrow implement, on the order of 5-8 meters wide, but is of limited value for wider implements because of the greater length and hence larger reciprocating mass. As the reciprocating mass increases, it shakes the header more and more which can cause failures.
In another arrangement, shown in U.S. Pat. No. 6,962,040 or in U.S. Pat. No. 7,478,522 a reciprocating knife is driven by gearboxes disposed on opposite ends of the implement. The knife may be a single long piece, or it may be made in two (or more) pieces and be driven 180 degrees out of phase. This arrangement requires two gearboxes, one on each end of the implement, and two elongate drive shafts extending from the middle of the implement to the two ends. Each reciprocating knife is about half the width of the implement. The two reciprocating knives are of generally the same size and reciprocate 180 degrees out of phase. As a result, the oscillations tend to cancel each other out. The arrangement requires two drive shafts and two gear boxes, one for each side of the implement.
Another arrangement, shown in US 2007/0204586 and in U.S. Pat. No. 5,497,605 drives a reciprocating knife from a central position disposed in the lateral middle of the implement. In the '605 patent, a drive shaft extending forward over the center conveyor of a draper platform, drives a crank at the front of the implement in a circular motion. This arrangement is disposed above and blocks crop flow onto the center conveyor. In addition, two rods that are coupled to the crank extend laterally outward and downward from the elevated crankshaft to two reciprocating knives to drive the knives. This reduces the weight of the reciprocating knife arrangement by providing one common drive mechanism and by avoiding the drive shafts that extend across the entire width of the implement. Unfortunately, it elevates the drive mechanism above the conveying mechanism and blocks the flow of crop from the cutter bar onto the conveying mechanism.
What is desired therefore is a drive mechanism for driving at least one reciprocating knife of an agricultural implement that does not require the addition of large gearboxes at the ends of the platform and additional (or longer) drive shafts to drive them. What is also desired is an arrangement that avoids the crop flow blocking structures disposed above the conveying mechanisms. What is also desired is a drive mechanism that takes up less space by disposing at least part of the drive mechanism within the endless belts. It is an object to provide all of these advantages in one or more of the independent and dependent claims provided below.